Ropes, cordage and twine



United States Patent 3,205,649 RQPES, CORDAGE AND TWINE AlexanderNisbct, Birmingham, and Garry Wallace Penmore, Harrogate, England,assignors to Imperial Chemical Industries Limited, London, England, acorporation of Great Britain No Drawing. Filed Apr. 3, 1963, Ser. No.270,156 Claims priority, application Great Britain, Dec. 3, 1962,45,461/ 62 8 Claims. (Cl. 57-440) This invention relates to improvedropes, cordage or twines (hereinafter referred to simply as ropes andthe like) in particular to ropes and the like constructed wholly or inpart from long staple fibers of synthetic polymers.

During the last decade or so man-made fibers derived from syntheticpolymeric substances have been used to replace some of the naturalvegetable fibers traditionally used for making rope and the like.Hitherto such manmade fibers have been used by the rope or twine makerin the form of continuous filament yarns prepared by the synthetic fibermanufacturer. This arrangement is unfavorable for the rope maker whooften requires new and expensive machinery to deal with the new yarnsand whose preparing machinery, designed for use with the natural fibers,is made obsolete.

Although the man-made synthetic fibers in general possess superiorstrength and abrasion resistance compared with the natural vegetablefibers, they are considerably more costly than the natural fibers and,in the form of ropes and the like made of continuous filaments, have a2) number of disadvantages. For example the slippery feel isunattractive in use, particularly to those accustomed to handlingvegetable fiber ropes and the like.

A more serious disadvantage of all ropes made wholly from syntheticfilaments is in situations where friction is likely to develop heatsufficient to soften or melt the individual fibers. Under theseconditions the surface of the synthetic filament rope becomes smooth andglazed and the rope useless for its proper function.

We have found that much improved ropes and the like may be prepared fromsynthetic polymeric substances if these are spun into continuousfilaments of appropriate thickness and then cut into suitable lengthsprior to making the rope yarns and the ropes therefrom.

According to our invention we provide a process for the production ofropes and the like composed of 20 to 100% by weight of synthetic fibersand 0 to 80% of long vegetable fibers comprising spinning the rope yarnfrom a mixture of the said fibers and constructing the ropes and thelike in the usual way, characterised in that the synthetic fibers arecut to a length between 25 and 80 inches and have a thickness between0.001 and 0.020 inch.

The process of our invention offers a number of advantages overprocesses already described for producing ropes and the like from eithernatural long vegetable fibers or continuous synthetic filaments. One ofthe most important advantages is that the synthetic fibers of ourinvention may be processed, either alone or mixed with the naturalfibers, directly on the usual machinery used for preparing and spinningnatural long vegetable fibers into yarn and for this reason blendingwith the natural fibers to produce a uniform yarn is simply effected.Furthermore by the process of our invention it is possible, without anymodification of the conventional process to produce a yarn of theapproriate size for construction of twine, cord or rope, whereas withcontinuous filament yarns of synthetic polymers a number of additionalplying operations are required to produce an adequate yarn.

In the production of ropes and the like a number of plying-with-twistingoperations are required. In each of these operations, because it isundesirable or impossible to twist the structure sufficiently tocompletely prevent slip- 3,205,649 Patented Sept. 14, 1965 page ofindividual fibers over one another under tension, some of the inherentstrength of the fibers comprising the structures is lost. An importantadvantage of the process of our invention is that this loss of inherentstrength is substantially lower than that incurred in constructing ropeseither from natural long vegetable fibers, as for example sisal ormanila, or from continuous filaments of synthetic polymers. Thisreduction in lost strength, by the process of our invention occursmainly at the first plying stage, that is, at the stage of preparing thetwine or rope strand from the rope yarn and the improvement is carriedthrough to the final structure.

In a satisfactory rope it is desirable that the extension of the rope atthe safe working load (usually about 20% of the breaking load) should beabout 5%. However, as the extensibility of synthetic fibers is, ingeneral, appreciably higher than that of the natural fibers, ropes andthe like made from continuous filaments of synthetic polymers usuallyhave an extension of very much greater than 5% at the safe working load.Several attempts have been made to overcome this short-coming ofsynthetic continuous filament ropes by special constructions of the ropesuch as are described in British Patent 811,501 and US. Patent3,055,167. Also by reason of the very different extensibility of naturaland synthetic fibers ropes constructed from yarns comprising naturalfibers on the one hand and synthetic filaments on the other fail easilywhen stretched by fracture of the less extensible natural fiber yarnscomposing the rope. We have found that by constructing the ropeaccording to the present invention, the extensibility of the final ropeis brought down to the desired value. The following table which givesthe properties of typical ropes of three inches circumference preparedfrom polypropylene in continuous filament (5 denier per fila ment) andlong staple (40 inches long and 0.005 inch diameter) forms illustratesthe improvement obtained by the process of the present invention.

We have also found that ropes and the like prepared according to ourinvention from mixtures of natural and synthetic fibers have a number ofadvantages over those prepared from all natural or all synthetic fibers.For example blending of the natural fibers with the stronger syntheticfibers improves the strength of the product over that of a comparableall vegetable fiber product, to an extent dependant upon the proportionof synthetic fibers used. Although this increased strength would beexpected to lead to a proportional increase in the life of the rope inuse, we have found, surprisingly, that ropes and the like, made by thepresent process have a life greatly in excess of this expectation. Forexample, a four strand rope of 3%" circumference made according to thisinvention from a 50/50 mixture of sisal and isotactic polypropylene (40"staple length 0.005 diameter fibers) has 20% less weight per unit lengththan an equivalent size of all sisal rope together with a 25%improvement in strength. This sisal/polypropylene rope in use as aquarter rope in deep sea trawling operations gave a lifetime of 6 to 8times that of the all sisal rope, very much in excess of expectation. Inanother usage two ropes of similar size were compared in use as tailropes in river barge towing which are subject to high abrasion togetherwith alternate wetting and drying cycles. One rope was all sisal and theother 50/50 sisal/polypropylene. The mixed rope gave a life of 6 timesthat of the all sisal rope.

A further advantage of the blended natural/artificial fibre ropes of thepresent invention is that such ropes do not swell to the same extent asall natural fiber ropes. Such swelling when the rope is subjected tosuccessive wetting and drying cycles leads to unlaying of the naturalfiber rope structure with consequent reduction of abrasion resistanceand life. This effect is substantially absent in the ropes of thepresent invention due to their reduced swelling propensity.

Also as some synthetic fibers, in particular those produced fromstereoregular polyolefines, have a low density, the density of theproduct may be controlled by adjustment of the proportions of naturaland synthetic fibers, so that the product will sink or float in Water asdesired. Ropes and the like constructed from a blend of natural andsynthetic fibers do not suffer from the deficiency of forming a glazedor smooth surface when subjected to frictional heat, for the naturalfibers serve to keep the fusible synthetic fibers apart and so preventthe formation of a continuous glazed surface. In this case also thewater retention of the wet natural fibers is often sufiicient to assistcooling or lubrication of the rope and further prevent fusing of thesynthetic fibers.

In order to assist preparation of the fiber blend and the spinning ofthe blend, in particular the separation of the synthetic fibers aftercompression into packages, we have found that it is desirable, if thecross section of the fibers is substantially circular, to impart a smallamount of crimp to the synthetic fibers of about -20 percent crimp asexpressed by the relation where L is the length of the filament with thecrimps present and L is the length of the same filament when extendedjust sufliciently to remove the crimps. We have also found that changingthe cross-sectional shape of the synthetic fibers has a beneficialeffect on the ease of processing the fibers, alone or mixed with naturalfibers into ropes and the like. Thus if fibers having a more or lessflattened cross section, as for example rectangular or square sections,are used there is no need to impartcrimp to the fibers in order toimprove the ease of processing. Whatever the cross-sectional shape givento the synthetic 4f the like. Among the most useful natural fibers arehemp, manila and sisal and of lesser importance are ramie and flax inthe longer forms.

The choice of synthetic fiber is governed to some extent by economicfactors but it is possible to use many of the commercially producedsynthetic fibers in'the process of our invention and we have found thatfibers prepared from stereoregular polyolefines, polyesters orcopolyesters polyamides, polyvinyl chloride, polyvinyl alcohol oracrylic polymers are very suitable. The very high strength coupled withlow density and moderate extension make the fibers prepared fromisotactic polypropylene very suitable for use in the process of ourinvention.

The natural and synthetic fibers are combined in as uniform a manner asis practical in the spinning operation to produce the yarns and when therope or the like has been completed no after treatment by heat isnecessary to stabilise the lay of the rope, such as is necessary when arope is made entirely of continuous synthetic filaments.

In a specific embodiment of our invention we have prepared a rope ofthree inches circumference from a 50/50 blend by weight of sisal andisotactic polypropylene fibers, the latter having a length of 40 inches,a diameter of 0.005 inch, and a tenacity of 7.0 grams per denier. Whenthis rope was subjected to a load equivalent to 75% of its breakingload, that is to a load of 3.9 tons, it was found upon close examinationafter releasing the load that the sisal fibers, which originally had alength of about 40 inches, were broken into short lengths of 1-2 inchescorresponding approximately to the distance between successive turns ofthe polyproylene in the twisted yarn. Thus it is apparentthat thegreater extensibility of polypropylene (18% approximately compared with2% for sisal) enables greater utilization of the strength of the naturalfiber before the latter is destroyed and the synthetic fiber assumes thefull load. By comparison an all sisal rope stretched to breaking pointwill exhibit a transverse fracture in which substantially all the fibershave broken at one point.

The following table illustrates the properties of ropes, all 3 inchescircumference, prepared on conventional long vegetable fiber spinningand rope laying machinery from the synthetic fibers and blends of thepresent invention. Also included for comparison are the properties ofropes of the same size. constructed from natural fibers or continuousmultifilament synthetic fiber yarns.

Rope Conversion Fiber Rope yarn Weight, CfllClGllCy, percent Fibertenacity, tenacity, lb./l20

gJden. gJden. fathoms Tenaelty, Strength, Fiber to Fiber to g./den. tonsrope yarn rope 1. All polypropylene, 40 x 0.005 inches diameter. 7. 0 6.9 3. 4 9. 4 156 99 49 2. 50/50 Sisal/polypropylene 40 x 0.005 inchesdiameter 3. 6 1. 8 6. 0 186 90 3. Manila 5. 1 2.5 l. 2 1 4. 5 206 24 4.'sal 4. 0 2. 2 1.0 2 4. 0 206 25 5. Polypropylene multifil. 5 d.p.i 8.06. 0 2. 9 8.0 143 37 6. Polyethylene terephthalate mult l, 5 d 6.0 4. 02.0 8.0 223 67 33 7. Nylon multifil, 5 d.p.f 8. 0 6.0 3.0 11.0 194 75 378. Polyethylene, 0.010 diam. mono 6.0 4. L 2. 2 5. 5 143 73 37 1 Minimumfor B.S.S. Grade 1. 2 Minimum B.S.S. value.

fibers it is essential that the thickness should be between 0.001 and0.020 inch. By thickness is here meant the diameter of a circular fiberor any linear cross-sectional dimension of non-circular or flattenedfibers. Fibers having a rectangular cross-section in which one dimensionis about three, times the other are particularly suitable.

Natural fibers suitable for use in the process of our invention are anyof those usually called long vegetable fibers and commonly used forproduction of ropes and In this table conversion efficiency is the ratioof breaking strength, for example of the rope yarn, to that of theinitial fibers expressed as a percentage. The size of the filamentscomprising the multifilament yarns is expressed in the usual wayasdenier per filament of d.p.f.

From the table the improvement in conversion eificiency obtained inropes made according to our invention, that is Examples 1 and 2, isclearly evident.

What we claim is:

1. Ropes and the like composed of spun rope yarn which is 20 to 100% byWeight of synthetic fibers blended with to 80% of long vegetable fibers,said synthetic fibers being cut of length between 25 and 80 inches andhaving a thickness between 0.001 and 0.020 inch.

2. Ropes and the like according to claim 1 wherein the synthetic fibersare selected from the group consisting of stereoregular polyolefines,polyesters, copolyesters, polyamides, polyvinvyl chloride, polyvinylalcohol and acrylic polymers.

3. Ropes and the like according to claim 2 wherein the stereorcgularpolyolefin is isotactic polypropylene.

4. Ropes the like according to claim 1 wherein the long vegetable fibersare selected from the group consisting of hemp, manila, sisal, ramie andflax.

5. Ropes and the like according to claim 1 wherein the synthetic fibersare crimped and have a substantially circular cross-section between0.001 and 0.020 inch diameter.

6. Ropes and the like according to claim 1 wherein the synthetic fibershave a more or less flattened cross-section.

7. Ropes and the like according to claim 6 wherein the synthetic fibershave a substantially rectangular crosssection in which one dimension isabout three times the other.

8. Ropes and the like according to claim wherein the crimp of saidsynthetic fibers is about 5-20% as expressed y where L is the length ofthe filament with the crimps present and L is the length of the samefilament when extended just sufficiently to remove the crimps.

References Cited by the Examiner UNITED STATES PATENTS 2,408,713 10/46Webb 572 X 2,420,565 5/47 Rugeley 281 2,616,239 11/52 Holcomb 571402,721,440 10/55 New 572 2,753,677 7/56 Slayter 572 3,016,683 1/62Simpson 57140 3,043,086 7/62 Hood 57157 X 3,055,167 9/62 Gaston 57140FOREIGN PATENTS 919,071 2/63 Great Britain.

OTHER REFERENCES Modern Textile Magazine (Rayon Publishing Corp.), June1956, pages 53, 54.

Practical Rope Maker, first edition, by George Lawrie, H. R. CarterPublications, Ltd., 1948; page 37.

MERVIN STEIN, Primary Examiner.

1. ROPES AND THE LIKE COMPOSED OF SPUN ROPE YARN WHICH IS 20 TO 100% BYWEIGHT OF SYNTHETIC FIBERS BLENDED WITH 0 TO 80% OF LONG VEGETABLEFIBERS, SAID SYNTHETIC FIBERS BEING CUT LENGTH BETWEEN 25 AND 80 INCHESAND HAVING A THICKNESS BETWEEN 0.001 AND 0.020 INCH.